1. Field of the Invention
The present invention relates to a fuel storage tank, to an aircraft having such a tank, and to a method of controlling such a tank.
The invention thus lies in the technical field of tanks, and more particularly in the field of aircraft fuel tanks
2. Description of Related Art
Conventionally, an aircraft has at least one tank for feeding fuel to a power plant. Pipework may be arranged for transferring fuel from the tank to an engine, or indeed to some other tank, for example.
The pipework opens out in the tank in a zone that is referred to for convenience as the “feed zone”. The pipework may comprise at least one pipe, and possibly also at least one booster pump.
Depending on the shape of the tank and on the position of the feed zone, a volume of fuel may be incapable of reaching the feed zone. This volume of fuel is sometimes referred to as the “non-consumable volume” insofar as this volume of fuel cannot be consumed by an engine.
In order to minimize the non-consumable volume in tanks, manufacturers include sloping surfaces in the bottoms of tanks in order to direct fuel towards the feed zone. Such surfaces are referred to as “slopes” for simplification. The slopes may be directed in the longitudinal direction and in the transverse direction relative to the vehicle.
In the context of an aircraft, the angle of the slopes may depend on the flight capacity of the aircraft, and more precisely on its capacity for sloping (attitude) and for angular acceleration/deceleration about its pitching and roll axes. Whatever the position of the aircraft, the feed zones must be capable of feeding the engines of the aircraft throughout a flight.
Under such circumstances, tanks may be made out of flexible material. By way of example, such a material may comprise a polyester backing with a mixture of elastomers. Foams inserted inside the compartment for a tank thus make it possible to provide the slopes on which the flexible tank rests.
For example, the slopes may have an angle lying in the range 5° to 9° in the longitudinal direction, and the angle may be about 3° in the transverse direction.
Nevertheless, installing foams and shaping the bottom corners of tanks leads to a non-negligible loss in the volume of fuel that can be carried. Furthermore, performance differences between different aircraft imply that the shape of each tank ought to be designed as a function of each particular aircraft, thereby preventing any type of standardization.
The technological background includes document U.S. Pat. No. 5,927,651.
That document discloses a fuel tank device having a deformable elastomer structure capable of adapting to the shapes of a compartment.
Document FR 2 294 913 discloses expandable fuel storage means capable of being expanded to take up a position in which it is located at least in part outside a zone of an airplane referred to as a “surface zone”.
Document U.S. Pat. No. 3,409,253 discloses a retractable tank system for an aircraft formed by rigid means surrounding a flexible surface for adapting to the quantity of fuel carried.
Also known are documents EP 2 135 805, U.S. Pat. No. 2,703,607, and U.S. Pat. No. 2,654,553.
Document EP 2 135 805 describes a container having an opening putting the inside of the container into fluid flow communication with the outside atmosphere. The container also houses a variable volume device.